This invention relates generally to the field of ground-water extraction for remediation of contaminated groundwater, particularly hydrocarbon-impacted groundwater. More specifically, it relates to an improved apparatus and method for vacuum-extracting groundwater from a well installed below the static groundwater table.
Increasing concern for the purity of groundwater has led to ever-stricter standards for the presence of contaminants, particularly hydrocarbons, in groundwater. In areas where the monitoring of groundwater for the presence of such contaminants is desired, or where remediation of hydrocarbon-impacted groundwater is mandated, it is necessary to install wells extending below the static groundwater table to extract groundwater.
An existing method employed to remediate groundwater is a process called "bioslurping." Bioslurping involves the placement of a small (1 in. or 2.54 cm diameter) extraction pipe, or "stinger," down into the well below the static groundwater table, and the application of a high vacuum (negative pneumatic pressure) to the above-ground end of the stinger. The depth from which water can be extracted is limited by the capacity of the vacuum pumps available, and even for moderate depths, powerful vacuum pumps must be employed, thereby increasing the cost of remediation. Furthermore, if the extracted water is contaminated by dissolved-phase hydrocarbons, the contaminants must be "stripped" from the extracted water by carbon filtration, leading to greater expense and the need to dispose of contaminated filters.
There has thus been a long-felt need for an extraction method that is less costly and more efficient, which reduces the need for liquid filtration, and that permits extraction from greater depths than has heretofore been practical without the use of a downhole pump.